1. Field of the Invention
The present invention relates to heterostructure semiconductor nanowires and a method for producing the nanowires. More particularly, the present invention relates to heterostructure semiconductor nanowires comprising semiconductor nanocrystal seeds and semiconductor nanocrystal wires grown in a selected direction from the surface of the semiconductor nanocrystal seeds wherein the semiconductor nanocrystal seeds have a composition that is different from that of the semiconductor nanocrystal wires. The present invention also relates to a method for producing the nanowires.
2. Description of the Related Art
Semiconductor nanocrystals produced by wet chemical processes can be utilized in microstructural devices due to their small size. In addition, the inherent characteristics of semiconductor nanocrystals can be controlled due to quantum confinement effects and the like, and as a result, various electrooptical properties can be induced and utilized. As a result, semiconductor nanocrystals have received a great deal of attention.
In particular, nanocrystals in the form of rods or wires advantageously afford the possibility of being able to use mobility characteristics of electrons in a particular direction along with the associated optical properties in that direction. For example, such nanocrystals can be used to induce a polarization phenomenon in microstructural devices in which they are employed. Much research has been conducted to synthesize such nanocrystals.
In this connection, Japanese Patent Laid-open No. 14-220300 teaches a method for producing nanowires comprising the steps of depositing microcrystalline silicon particles on the surface of a silicon substrate and heating the substrate to a temperature at which the surface of the silicon substrate is melted under a vacuum. The heating step generates surface segregation on the crystal surface of the microcrystalline silicon particles to allow a plurality of nanowires to grow thereon.
The problems of this method, however, are that both steps are carried out on the substrate using vapor deposition thereby causing an increase in production costs.
Further, Korean Patent Laid-open No. 2004-000418 proposes a nanowire comprising a first segment of a substantially crystalline material and a second segment of a material having a composition different from that of the first segment and joined to the first segment wherein at least one segment of the first and second segments has a substantially uniform diameter of less than approximately 200 nm. This patent publication discloses nanowires having two or more structures and suggests the possibility of using the nanowires in various applications.
However, although the patent publication proposes the basic concept regarding the structure of the nanowire, it fails to disclose detailed production processes, i.e., a process for controlling the reactivity of the second segment. Further, Japanese Patent Laid-open No. Hei 15-277029 introduces a method for manufacturing carbon nanotubes by disposing a nanocarbon material on a substrate and selectively growing carbon nanotubes almost perpendicular to the substrate. This patent publication is highly distinguished from the present invention in terms of the final products and processes employed.
Japanese Patent Laid-open No. Hei 16-122283 introduces a method for manufacturing a nanometer-sized microstructure comprising the steps of forming a material layer on a substrate, forming a pattern on the material layer using pyramidal particles, depositing a metal catalyst on the patterned material layer, peeling the material layer to form a patterned metal catalyst, and growing the patterned metal catalyst into a crystal. This patent publication is highly distinguished from the present invention in terms of the final products and processes employed.